Subject: Re: [PATCH net-next] selftests/net: packetdrill: add CONFIG_MAX_SKB_FRAGS=17

From: Willem de Bruijn <[email-masked]>
Date: Tue, 24 Mar 2026 10:53:37 -0400

Eric Dumazet wrote:
> Before adding tests about RWIN, enforce the default linux value
> for the number of fragments per skb.
> 
> With 17 fragments, sizeof(skb_shared_info) == 320.
> 
> With 45 fragments, sizeof(skb_shared_info) == 768.
> 
> Signed-off-by: Eric Dumazet <[email-masked]>
> ---
>  tools/testing/selftests/net/packetdrill/config | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/testing/selftests/net/packetdrill/config b/tools/testing/selftests/net/packetdrill/config
> index c4a19a78552111df690d2c97c0f3a8abe2176ada..8c739db4752c3abaaa8862ea2aeb661a2d5f0575 100644
> --- a/tools/testing/selftests/net/packetdrill/config
> +++ b/tools/testing/selftests/net/packetdrill/config
> @@ -1,6 +1,7 @@
>  CONFIG_HZ=1000
>  CONFIG_HZ_1000=y
>  CONFIG_IPV6=y
> +CONFIG_MAX_SKB_FRAGS=17
>  CONFIG_NET_NS=y
>  CONFIG_NET_SCH_FIFO=y
>  CONFIG_NET_SCH_FQ=y

Why do we need to make this explicit, if it is the default?